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Mike S.
Mike S., ASE Certified Technician
Category: Chrysler
Satisfied Customers: 7568
Experience:  ASE Certified Master Technician
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Alternator went out, replaced it and then it blew again, the

Customer Question

Alternator went out, replaced it and then it blew again, the repair guy said it was because the battery was too low. He rebuilt the bridge and I installed it again, this time I checked to see if it was putting out voltage, which it was not, only 12v from battery. Not sure what to do.
Submitted: 1 month ago.
Category: Chrysler
Customer: replied 1 month ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call.
Customer: replied 1 month ago.
Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Mike S. replied 1 month ago.

Hi, I am Mike, welcome. I'm reviewing your question.

Customer: replied 1 month ago.
ok
Expert:  Mike S. replied 1 month ago.

I want to pull up the wiring diagram and want to be sure. With that done said, I see there are actually 2 different 2.7 engines, one with a code of R and one with a T, so if you could tell me the 8th digit of the vehicle vin number if it's an R or a T?

Customer: replied 1 month ago.
T
Expert:  Mike S. replied 1 month ago.

Ok, got it. Now, the red wire at the alternator make sure it is has 12 volts with key off engine not running.

Then check the ground wire, it's the black/tan wire at pin 1 of the alternator, so just move your voltmeter ground test lead to that black/tan wire while keeping the positive on that red wire if it had 12 volts before and it should still rad 12 volts.

Then start the engine, rev it up to about 2,000 rpm and check the voltage again at the red wire and you can ground the voltmeter wherever, on that black/tan or a metal ground or the negative battery post but now the voltmeter should read like 14 volts at the back of the alternator at 2,000 rpm. If not, let me know. If it does check again the voltage making it to the positive battery post. If it is only 12 there, then that red wire/cable from the alternator to the positive battery post is bad.

Expert:  Mike S. replied 1 month ago.

If it still only puts out 12 volts at the back of the alternator at the red wire and everything else checked out ok, then the PCM driver obviously isn't providing the ground for the field. So if that is the case begin by checking those fuses, #14 in the PDC at left front fender and the 325 same spot. If they both are good, try a new auto-shut down relay, also in the PDC. make sure you use the voltmeter when checking the fuses, too and the #14 should be hot on both sides even with key off, but the #25 is powered from the auto shut-down relay, so the key will most likely have to be on run and maybe even with the engine running.

Customer: replied 1 month ago.
I have 12 volts at red wire on alternator. I do not understand the next step, do I keep the red lead on the alternator red wire and the black lead just touching the plastic coated wire on the pin?
Expert:  Mike S. replied 1 month ago.

Here is that wiring diagram,

Yes, keep the voltmeter positive lead on the red wire and move the voltmeter negative test lead to the black/ tan wire cause that is the ground wire. That would test to make sure the ground wire is ok and grounding.

Customer: replied 1 month ago.
I do not show any voltage when I do that
Customer: replied 1 month ago.
there are two wires on that pin and neither show voltage, if i am checking in the right place
Expert:  Mike S. replied 1 month ago.

Ah ha. That means that ground is bad. Maybe it is just unhooked at the other end. Check at the left front strut tower for the ground, it should have a black wire cause the wire changes color.

Expert:  Mike S. replied 1 month ago.

wait, You are not supposed to be checking voltage there, that is a ground. Place the negative voltmeter lead on that black/tan wire at the positive test lead where it was on that red wire.

Customer: replied 1 month ago.
im not sure how what you are asking me to do is different, i have the red lead on alternator red power that goes to battery, and then i take black lead and touch it to the plastic coated wire coming off the 2 wire pin on the alternator
Expert:  Mike S. replied 1 month ago.

Yes, that is it, the black/tan wire. You did this nd now the voltmeter reads 0 volts?

Customer: replied 1 month ago.
0 volts, also tried it with the car on and still 0 volts. I did find the ground by the strut, there are two black wires that come together and are bolted down, appear to be nice and tight
Expert:  Mike S. replied 1 month ago.

Check this spot for that G103 ground and see if it is unhooked. If not, unhook it and unhook the black/tan wire a the alternator and use an ohmmeter on both ends and check if it makes continuity or not.

Expert:  Mike S. replied 1 month ago.

Ok, you found it, now check it with an ohmmeter.

Expert:  Mike S. replied 1 month ago.

Or if you don't have an ohmmeter just hook your voltmeter back up to check that red wire and this time run a jumper wire from that black/tan wire to ground or the negative battery post and see now if the alternator puts out 14 volts when reved to 2,000 rpm. If so, that ground is bad.

Customer: replied 1 month ago.
I have ohms on my voltmeter, but not sure how to check ohms, or which of the black wires i check on the strut
Expert:  Mike S. replied 1 month ago.

Check them both. Set the meter on OHMs, the lowest setting. Say like around 5 ohms. Or whatever is closet to that. Then touch the leads together, look at the meter that is what it would show if the wire is intact when you use it on the wire. now move the test leads apart, this shows an open or bad circuit. Now test that wire with the ohmmeter.

Customer: replied 1 month ago.
when i put the leads together on ohms is it supposed to say 0?
Expert:  Mike S. replied 1 month ago.

Yes, the must be a digital ohmmeter then. Then 0 is what it is supposed to say when checking both ends of that wire, or damn close to 0 maybe like 5 ohms at the most. So, let me know.

Customer: replied 1 month ago.
i just touch the leads directly to the plastic coated wires?
Expert:  Mike S. replied 1 month ago.

No, you have to touch the test lead to either the metal end of the wire or any copper wire strands that might be exposed, Not just the plastic cause that is probably an insulator.

Is the plastic where you put the test lead when using the voltmeter? If so, you must touch the metal end of the wire, or if there is none, then you will have to poke through the wire insulation and get to that copper wire strands.

Expert:  Mike S. replied 1 month ago.

but when using the ohmmeter the wire has to be disconnected anyhow at the alternator, so you should not have to poke through, just touch it to the end of the wire at the metal end.

Customer: replied 1 month ago.
I was testing on plastic coated wire, I thought I asked that a few times. so i need to poke the test lead through the plastic coating of the wire?
Customer: replied 1 month ago.
there is no bare wire on the pin of the alternator
Expert:  Mike S. replied 1 month ago.

Yes, then you will have to poke through, but before that, check those fuses, maybe it is just a fuse. I hate to poke through wire insulation cause water can get in. If you must, make sure you tape it up afterward with electrical tape.

Customer: replied 1 month ago.
im not sure i can poke it through, the two wires on the alternator or pretty small, the ground wires by strut are big enough but not the one on the laternator
Expert:  Mike S. replied 1 month ago.

Check them fuses now.

Customer: replied 1 month ago.
im not sure we have ever tested the ground accurately
Expert:  Mike S. replied 1 month ago.

No we did not. Check the fuses first.

Customer: replied 1 month ago.
how do i check a fuse with voltmeter
Expert:  Mike S. replied 1 month ago.

ground the negative to a metal ground and touch the positive to each side of the fuse where the metal is exposed on the edge of the fuse.

Customer: replied 1 month ago.
how do i know which fuse to check, they are not numbered
Expert:  Mike S. replied 1 month ago.

Are the labeled in any way at all?

Customer: replied 1 month ago.
just with the amps, 10, 20, etc
Expert:  Mike S. replied 1 month ago.

This should help, it shows the numbers

Customer: replied 1 month ago.
check 25 and 14?
Expert:  Mike S. replied 1 month ago.

Yes. First just look at both t see if either are blown. Then test both sides, 14 hot all the time and 25 with key on run.

Customer: replied 1 month ago.
both fuses look good, i dont understand how i am to test them. I take them out and put negative on a ground and positive one of the metal tips of the fuse?
Expert:  Mike S. replied 1 month ago.

I tell you what, just try swapping that auto shut down relay with the headlamp washer relay, then go back and check if the alternator is putting out 14 volts now at 2,000 rpm.

Expert:  Mike S. replied 1 month ago.

If there is no metal tips exposed on the edges of the fuse, then you would have to remove it and test the empty socket, but then again, only one terminal in the socket can be hot that way

Customer: replied 1 month ago.
we seem to be getting farther away from solution
Customer: replied 1 month ago.
switched relays, still nothing
Expert:  Mike S. replied 1 month ago.

What do you mean still nothing? The voltmeter has to read something, is it 12 volts now at the red wire or is it really 0 volts?

Customer: replied 1 month ago.
12 yes, looking for 14
Expert:  Mike S. replied 1 month ago.

Ok, about all you can do then install new fuses in those 2 spots, hope for the best and if it still don't work, have someone retrieve those trouble codes cause you may be looking at a faulty PCM.

Customer: replied 1 month ago.
i have a code reader and do not show any codes, just battery light comes on
Customer: replied 1 month ago.
how do i know my alternator ground is good, we never checked that did we?
Customer: replied 1 month ago.
or is it not relevant?
Expert:  Mike S. replied 1 month ago.

Disconnect both ends and use the ohmmeter and you have to touch the metal ends on both ends.

Customer: replied 1 month ago.
I have to pull the black wire from the pin? How will I get it back on?
Expert:  Mike S. replied 1 month ago.

What black wire and from what pin?

Customer: replied 1 month ago.
I thought we were talking about ground wire on alternator again
Expert:  Mike S. replied 1 month ago.

That isn't a black wire at the alternator is it? isn't it a black/tan wire?

Customer: replied 1 month ago.
there are two wires on the pic, a black and a green
Customer: replied 1 month ago.
pin
Customer: replied 1 month ago.
i can send picture if that helps
Expert:  Mike S. replied 1 month ago.

Ok, yes than the black wire, I suspect maybe you cannot see the tan stripe.

Expert:  Mike S. replied 1 month ago.

Yes a photo, please

Customer: replied 1 month ago.
these are only wires to my alternator other than battery wire
Expert:  Mike S. replied 1 month ago.

Yeah, I see the tan stripe on that black wire but it is very faint, but it is there. That is the one.

Customer: replied 1 month ago.
im not sure how to test the groung, cannot stick my lead through that wire, it is too thin
Expert:  Mike S. replied 1 month ago.

That plastic piece may unclip an open a bit so you can test, try to open that plastic piece.

Customer: replied 1 month ago.
you are saying unlplug the pin from the alternator?
Expert:  Mike S. replied 1 month ago.

Unplug it if you are going to use the ohmmeter but if using the voltmeter the wire will have to be still hooked up, I thought that maybe the plastic piece was just a protector or sorts that could be opened up to expose the wire end.

Customer: replied 1 month ago.
does not open, so i have it unplugged, now what
Expert:  Mike S. replied 1 month ago.

Disconnect that black wire at that ground g103 and use the ohmmeter and check if that ground wire is open or closed. Actually, for now just leave that G103 hooked up and test the resistance using the ohmmeter between the black/tan wire at the alternator and the battery negative post. Like that it should read less than 5 ohms.

Customer: replied 1 month ago.
I tested the ground to the black wire connector in pin and have 4ohms so that looks to be good
Expert:  Mike S. replied 1 month ago.

Yes.

Customer: replied 1 month ago.
also 4-5 ohms from black connector wire in pin to negative battery post
Expert:  Mike S. replied 1 month ago.

I believe if you momentarily jump that green wire to a metal ground while the engine is idling, the alternator should put out the maximum voltage, so do you want to try that?

Expert:  Mike S. replied 1 month ago.

If when you do this and it puts out over 14 volts, then I would summize that the PCM is bad.

Customer: replied 1 month ago.
how do i jump the green wire?
Customer: replied 1 month ago.
im guessing that is harder than it sounds
Expert:  Mike S. replied 1 month ago.

First make a jumper wire. Then if you have to unhook that connection at the back of the alternator if you have no exposed metal on the wires. Then you would actually have to make 2 jumper wires, cause you will have to connect that black/tan wire back to where it is supposed to go, Then you can just jump where the green wire connects to the alternator and jump it to a metal ground, so you can just leave the green wire disconnected from the harness for now and the PCM.

Expert:  Mike S. replied 1 month ago.

Like this it will completely bypass the PCM.

Customer: replied 1 month ago.
that made no sense to me, it has to be simple for me, does the plug need to be back in the alternator?
Expert:  Mike S. replied 1 month ago.

No, leave it off. make 2 jumper wires. One that will hook up to the end of that black/tan wire and the other end of the jumper wire plug onto the spot on the alternator where that black/tan wire goes. Then with a second jumper wire and most likely a much longer one, make it so it plugs into where that green wire goes on the alternator and attach the other end of the long jumper wire to a metal ground or the battery negative post if you make it long enough to reach that.

Expert:  Mike S. replied 1 month ago.

Are you making jumpers?

Customer: replied 1 month ago.
going to have to stop, will need to buy little clamp to connect wire onto the post in the alternator, probablyl tomorrow
Expert:  Mike S. replied 1 month ago.

ok